Dithiophosphoric acid esters and their preparation



DITHIOPHOSPHORIC ACID ESTERS AND THEIR PREPARATION Gerhard Schrader, Opladen, Germany, assignor to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Gerniany No Drawing. Application October 11', 1956 Serial No. 615,234"

Claims priority, application Germany October 13, 1955 4 Claims. (Cl. 260-461) This invention relates to and has asits object the provision of new and useful dithiophosphoric acid esters, more particularly those of the following formulai In this formula R stands for alkyl, especially lower alkyl radicals, A and B stand for a'kylene especially lower alkylene chains and Ar means aryl especially phenyl radicals or substituted phenyl radicals (particularly those which are halo, nitro or lower alkyl substituted).

Many thiophosphoric acid esters have become very important in the field of insecticides or generally pesticides during the last years and intensive workhas been done in finding more efiective compounds especially such compounds with comparable lower toxicity against mammals.

In accordance with the present invention a new class of valuable insecticides has been found which corresponds to the above described formula; more particularly this invention is concerned with compounds of the formula:

ROS

in which R, A and B have the significance as given before. Examples of such compounds are the 0.0-dimethyl, 0.0-diethyl, 0.0-dipropyl, 0.0-diamyl-dithiophosphoric acid which carry as an ester radical at the thiol-sulfur the benzylmercaptoethyl-, benzylmercaptomethyl-, p-rnethylbenzylmercaptoe-thyl-, p-chlorobenzylmercaptoethyl-, pnitrobenzylmercaptoethyl-, 3 chloro 4 nitrobenzylmercaptoethyl-, benzylmercaptopropyl-, benzylmercaptoisopropyl-, phenethylmercaptomethyl-, phenethylmercaptoethyl-, p chlorophenylethylmercaptoethyl-, pnitrophenylethylmercaptoethyl-, phenylpropylmercaptoethyl-group and the like.

The preparation of these compounds may be accomplished by reacting the corresponding aralkylmercap-toalkylhalide with the appropriate 0.0-dialkyldithiphosphoric-salt (or the free acid in the presence of acid binding agents) exactly as described in U.S. Patent No. 2,759,010. The reaction may typically be shown by the following equation:

This reaction, as described in U.S. Patent 2,759,010 is preferably carried out in inert organic solvents at slightly elevated temperatures. Especially suitable for nited States Patent 0 splitting ofi hydrogen-halide which escapes.

Z this reaction are the ammonium salts of dithiplio'sphoric acid esters.

It is, however, also possible to obtain these new esters by reacting the free OLO-diaikyl-dithiophosphoric acids with the corresponding aralkylmercaptoalkylhalide, thus This reaction is described in copending application of Gerhard Schrader et a1. Serial No; 554,378yi1titled Process for the Manufacture of Neutral Thiono-ThioLPhosphoric Acid Esters and filed November 20, 1955. Stillanother method for the preparation ofthe inventive c dmpfiuids mammals. They may beusedin the same mannei-f as" other known' phosphoric insecticides, i.e. in a concentra' tion from about 0.00001%' to about 1%, d'ilute'cl or ex tended with suitable solid or liquid carriersflordfluents: Examples of such solid carriers are talc, chalk; bentonite', clay and the like, as liquid carriers there may be mentioned, water (if necessary with commercial emulsifiers) alcohols, especially lower alcohols such as methanol or ethanol, ketones, especially lower ketones such as acetone or methylethylketone, liquid hydrocarbons and the like. The new compounds may furthermore be used in combination with each other or with known insecticides, fertilizers, etc.

The following example illustrates the possibilities how to prepare'the-inventive compounds, without, however, restricting the present invention thereto.

Example C2H50 S CzHsO 38 g. B-chloroethyl-benzyl-mercaptan are added dropwise at a temperature of C. to a suspension of finely divided 0.0 diethyl dithiophosphoric acid ammonium salt in 60 ml. butanol. The temperature is kept for further 15 minutes at 90 C. and then the reaction mixture is cooled. The precipitated ammonium chloride is removed by filtration or sucked off and then the butanol is distilled off. The remaining crude ester is purified by distillations, thus yielding 47 g. of the above ester, boiling at 0.05 mm. Hg at 171 C.

If instead of 0.0-diethyldithiophosphoric acid the equivalent molecular amount (35 g.) of the dimethyl ester is used there is obtained the corresponding dimethyl ester of the formula:

CHsO S This methyl ester distills at 0.4 mm. Hg at (with partial decomposition).

By using the equivalent molecular amount of p-chlorobenzyl-B-chloroethylmercaptan there is obtained the corresponding S-ethylmercapto-(p-chlorobenzyl) ester of the formula:

In an exactly analogous manner there may be obtained the following new compounds:

I 1. A dithiophosphoric acid ester of the forrnula I P-S-A--SB-Ar I I R0 in which R stands for an alkyl radical having one to four carbon atoms, A and B stand for a lower alkylene chain and Ar stands for a member selected from the group consisting of phenyl, halophenyl, nitrophenyl, and lower alkylphenyl.

t s c,m s m Cz 5O r 3. A dithiophosphoric ester of the formula C1130 vs SC2Hr-S-CH2 I CHaO 4. A dithiophosphoric ester of the formula CzH O s (hHaO I References Cited in'the file of this patent UNITED STATES PATENTS Schrader Oct. 16, 1951 

1. A DITHIOPHOSPHORIC ACID ESTER OF THE FORMULA 